1. Field of the Invention
The present invention relates to a compound-type energy generation system which combines a Stirling engine and a fuel cell, whereby mechanical energy and electrical energy can be generated efficiently.
2. Description of Background Art
A compound-type power generation system including a combination of a fuel cell and a gas turbine is disclosed in xe2x80x9cProceedings of The 9th SOFC Research Presentation Meeting, 106Bxe2x80x9d. The compound-type power generation system is so constructed that an unreacted fuel discharged from a fuel cell which performs power generation by a chemical reaction of a fuel is mixed with air, before being combusted in a combustor, and the combustion gas is utilized as a driving source for the gas turbine and a heat source for a fuel reformer, whereby electric power generated by the fuel cell and electric power generated by a generator driven by the gas turbine are efficiently obtained.
The above-mentioned prior art has a problem in that the efficiency of the gas turbine is conspicuously lowered in a partial load condition, so that the purpose of the use of the system is limited to a system capable of steady operation such as a large scale power generation system.
The present invention has been made in consideration of the above-mentioned circumstances, and, accordingly, it is an object of the present invention to efficiently generate mechanical energy and electrical energy by a combination of a Stirling engine and a fuel cell.
In order to attain the above object, according to the present invention there is proposed a compound-type energy generation system including a combination of a Stirling engine and a fuel cell, characterized in that an unreacted gas discharged from the fuel cell is combusted in a heater of the Stirling engine.
According to the above constitution, the unreacted gas discharged from the fuel cell is combusted in the heater of the Stirling engine, so that it is possible to first supply a fuel to the fuel cell to generate electrical energy, and then to use the heat generated by combusting the unreacted gas not reacted in the fuel cell in the heater for generating mechanical energy in the Stirling engine, whereby electrical energy and mechanical energy can be efficiently generated through wasteless utilization of the fuel. In addition, by the combination of the Stirling engine and the fuel cell, the system as a whole can be reduced in size.
According to the present invention, there is proposed a compound-type energy generation system wherein the combustion of the unreacted gas is a catalytic combustion.
According to the above constitution, the unreacted gas discharged from the fuel cell is subjected to catalytic combustion in the heater of the Stirling engine, so that the heater can be reduced in size as compared with the case of using flame combustion, and the limitation as to the positioning of the Stirling engine can be reduced because convection of the unreacted gas due to a flame is absent.
According to the present invention, there is proposed a compound-type energy generation system wherein the periphery of the heater of the Stirling engine is surrounded by the fuel cell which is arranged in an annular-shape.
According to the above constitution, the periphery of the heater of the Stirling engine is surrounded by the annular-shaped fuel cell, so that it is possible to cause the reaction heat generated by the fuel cell to act effectively on the heater, to further elevate the temperature of the heater and thereby to enhance the performance of the Stirling engine.
According to the present invention, there is proposed a compound-type energy generation system wherein the fuel cell is a solid electrolyte type fuel cell.
According to the above constitution, the solid electrolyte type fuel cell is adopted, whereby a reformer for fuel is unnecessitated, and the system can be simplified and reduced in size.
According to the present invention, there is proposed a compound-type energy generation system wherein a Seebeck device is disposed in an exhaust passage of the heater of the Stirling engine.
According to the above constitution, the Seebeck device is disposed in the exhaust passage of the heater, so that it is possible to generate electrical energy by recovering the thermal energy of the exhaust gas of the heater.
Incidentally, the solid electrolyte type fuel cell FC in the embodiment corresponds to the fuel cell in the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.